He should have let his phone just ring off the hook when Donald Trump called repeatedly to offer him a job in his administration as secretary of Housing and Urban Development.

He should have run away as fast as he could the moment he realized that there were “two different Donald Trumps,” which is how Carson once described the president. As an expert on matters of the brain, the renowned neurosurgeon should have known better than to fall into the grips of a deviant with a split personality.

Carson should not have believed for a moment that the opponent he says he eventually came to think of as “very cerebral, sits there and considers things very carefully” could actually overtake “the one you see on the stage.”

For Trump, life is a performance. There is no curtain between fantasy and fact.

Had Carson walked away when he had the chance, he and his family would not be, as he said last week, “under attack by the media questioning our integrity and ethics.”

Had he acknowledged his lack of experience in the affairs of government and turned Trump down, he could have avoided the embarrassing fiasco that has come to define his tenure at HUD.

He would not be accused of wasting $31,000 in taxpayer money on a dining room set for his office at a time when Trump is trimming $6.8 billion from the budget of the department that oversees low-income housing for the elderly and poor.

Had he said no to Trump, HUD’s inspector general would not be looking into nepotism at the agency, questioning whether Carson’s son, Benjamin Jr., and other family members had inappropriate roles in managing department affairs.

If Carson said no to Trump in the beginning, he would not have been tempted to try and bend the rules as far as his boss has in the White House. Carson would not have had the chance to enlist the help of his son after Trump opened the door by enlisting the help of his daughter.

Indeed, had Carson not gotten tied up with Trump, he might have been able to redeem himself as American visionary — lauded for his determination not to let adversity stand in the way of his success.

Ben Carson could have been a role model whom people looked up to.

But he fell under Trump’s debilitating spell, stepping freely into his abyss of lies, dishonor and deceit from which there is no route for redemption.

Anyone who falls for such a lure is a fool.

By most standards, Carson would be considered a brilliant man. It is no small feat to work your way out of poverty to become an acclaimed pediatric neurosurgeon. To graduate from Yale University and then go on to medical school. To be named director of pediatric neurosurgery at Johns Hopkins Hospital at age 33, at the time the youngest physician in the country to hold such a position.

And to gain international prominence after successfully performing surgery to separate 7-month-old twins who were born joined at the head.

That is the stuff of which heroes are made. But Carson is anything but a hero.

Mark Wilson / Getty Images

HUD Secretary Dr. Ben Carson speaks before U.S. President Donald Trump signed a proclamation to honor Martin Luther King, Jr. day, in the Roosevelt Room at the White House, on January 12, 2018 in Washington, DC.

HUD Secretary Dr. Ben Carson speaks before U.S. President Donald Trump signed a proclamation to honor Martin Luther King, Jr. day, in the Roosevelt Room at the White House, on January 12, 2018 in Washington, DC. (Mark Wilson / Getty Images)

Under Trump’s tutelage, he has become a political joke, a flunky, a man who was so anxious to follow Trump’s drumbeat that he could no longer hear his own.

It would be wrong to blame Carson’s unraveling entirely on Trump, though. Much of it is Carson’s own doing. He made the mistake of believing his own hype.

Conservatives loved his fabled story of having pulled himself up by the bootstraps. They loved citing him as an example of what African-Americans could achieve if someone just ripped the rug of government dependency out from under them.

Carson was the confirmation Trump and others needed to prove once and for all that African-Americans who struggle in this country do so because of their own lack of drive and ineptitude.

It relieved them of any responsibility to reach back to help those left behind.

That’s why Trump needed Carson for this particular job. He was supposed to spread this flawed philosophy throughout impoverished America.

It took a year for Carson to realize that it would not be that easy. It took him that long to realize that “there are more complexities here than in brain surgery,” as he recently told The New York Times.

Perhaps Carson also will find that everything he thought he knew about Trump was a lie. Perhaps he will understand that Trump never intended to make HUD a viable tool for improving the lives of the underserved.

Perhaps Carson will know that he was just a pawn. Perhaps he will see that he would have been a great man had he just said no.